Apparatus for obtaining hydrogen

ABSTRACT

A hydrocarbon and air mixture or a hydrocarbon and oxygen mixture is incompletely catalytically burned, in a highly porous sinter block or stone containing nickel or platinum. The block is provided with passage openings. The thus obtained gas mixture which consists, mainly of CO and H2 is brought by means of at least one quenching with H2O down to temperatures of 500* to 150*C and subsequently reacted with the formed water vapor in sinter blocks which are highly porous, contain conversion catalysts and are provided with preferably parallel passage openings.

United States Patent 1191 Koch .1451 Mar. 19, 1974 1 APPARATUS FOR OBTAINING HYDROGEN [75] lnventor: Christian Koch, Erlangen. Germany [73] Assignee: Siemens Aktiengesellschait,

Munich,,Er1anger & Berlin, Germany 22 Filed: DCC.'15,1970 21 Appl.No.:98,264

[30] Foreign Application Priority Data Dec. 24, 1969 Germany 1964810 52 11.5. c1. 23/288 R, 23/288 F. 23/288 1-1. 23/288 K, 48/107. 423/213. 423/655.

51 1m. (:1. B0lj 9/04, COlb 2/10 [58] Field 61 Search. 23/212. 212 A. 277 c. 288 R, 23/288 H.288 K. 288 M. 289, 277 12,281

' 197 R. 196R.215 US [56] ReferencesCited UNITED STATES PATENTS 3.441.359 4/1969 Keith et a1. 431/328 2.465.235 3/1949 Kubicek 23/213 2.482.866 9/1949 Phinney 252/373 2.934.407 4/1960 Simonek et a1. 23/213 L257258 9131U1Ll11512 1.904.908 4/1933 Voorhees 23/213 3.010.807 11/1961 Christensen et a1. 23/213 X 1.967.665 7/1934 Feiler et a1. 23/288 R UX 2.956.864 10/1960 Coberly 3.172.251 3/1965 Johnson 23/277 C 3.679.372 7/1972 Hartman. Jr. et al 23/277 C FOREIGN PATENTS OR APPLICATIONS 1.193.202 5/1970 Great Britain 23/213 1.152.385 8/1963 Germany 23/213 265.989 9/1927 Great Britain 23/213 Primary Examiner-Joseph Scovronek Attorney. Agenl. 0r Firml-lerbert L. Lerner [57] ABSTRACT A hydrocarbon and air mixture or a hydrocarbon and oxygen mixture is incompletely catalytically burned, in a highly porous sinter block or stone containing nickel or platinum. The block is provided with passage openings. The thus obtained gas mixture which consists. mainly of CO and H is brought by means of at least one quenching with 11 0 down to temperatures of 500 to 150C and subsequently reacted with the formed water vapor in sinter blocks which are highly porous. contain conversion catalysts and are provided with preferably parallel passage openings.

9 Claims, 1 Drawing Figure l APPARATUS FOR OBTAINING HYDROGEN My invention relates to a method for obtaining hydrogen.

A process is known, from my application Ser. No. 56,885, filed July 2], i970, for flameless combustion of gases in porous sinter blocks, wherein a mixture of hydrocarbons and oxygen or a hydrocarbon and air mixture is burned in a highly porous sinter block, provided with passage openings. said sinter block containing nickel or platinum.

The insertion of suitable catalysts into the porous sinter block accelerates the reaction speed of the hydrocarbon and air mixtures so that the surface temperature ofthe sinter block doubles and the sinter block load capacity increases 40 times. Thus. with benzene vapor and air mixtures, sinter blocks containing nickel may reach temperatures of 900 to l,400C, and sinter blocks containing platinum may reach temperatures up to l.650C.

In this method, the hydrocarbons employed may easily be evaporated by preheating. Particularly suitable are hydrocarbons of formula C H to C,,H that is those hydrocarbons which are liquid at room temperature.

The original materials are installed when nickel catalysts are used, preferably in a stoichiometric ratio, for example. according to the equation:

wherein deviations in the oxygen content are possible, both upward and downward. A permanent excess of oxygen should be avoided in a nickel catalyst due to a danger ofinactivation from an irreversible oxidation. If the hydrocarbons are combusted with a deficiency of air, the fuel gas forming thereby may, if necessary, be combusted afterward with secondary air.

In platinum containing sinter blocks, the ratio of the original products is adjusted to the desired temperature or to the desired reaction process. Hence. combustion can be effected with a deficiency as well as with an excess of air. During the combustion with nickel containing as well as of platinum containing sinter blocks, oxygen may be substituted for the air producing a further increase in temperature.

The sinter blocks used for flameless combustion comprise a highly porous material which is essentially open-pored, for example a sintered magnesium aluminum oxide. They comprise additional, preferably parallel positioned passage openings. The passage openings may have a pore radius of approximately 0.5 mm, whereby about 40 passageopenings are provided per 1 cm of sinter block area. The entire pore volume should be at least 50 volume-percent, but is preferably about 65 volume-percent. The additional passage openings, first ofall. prevent clogging of the sinter block by contamination and, secondly, facilitate and increase the throughput of the gas mixture considerably.

The installation of the nickel or platinum catalyst is carried out in a known fashion through impregnation of the sinter block with a nickel salt solution, or a platinum salt solution, or with a platinum acid solution. Suitable nickel salts are, for example, nickel acetate, nickel carbonate, nickel formate, etc. The platinum is preferably inserted into the sinter block in form of an aqueous solution of H [PtCI Other platinum com pounds may also be used in lieu of H [PtCl,,]. The

amount of nickel in the sinter block may amount to l mg/cm to 200 mg/cm, but may also be higher. An increase in sinter block load capacity could no longer be observed with nickel quantities of 500 mg/cm, 800 mg/cm and above. Particularly suitable were found to be nickel quantities of 10 to mg/cm. The platinum content is about 0.] to mg/cm but preferably 5 to 10 mg/cm. It is essential for the selection of the catalyst salt that the salt be easy to dissociate thermally. After drying in air or, if necessary, with heat, the sinter block may immediately be installed as a radiation surface into an appropriate heating chamber.

If a mixture of benzenevapor and air in a stoichiometric ratio is combusted in a sinter block wherein 50 mg/cm nickel are uniformly distributed, one obtains, depending on the radiation ratio and gas mixture, a surface temperature of about l,lOOC to 1,450C and when combustion takes place in a sinter block containing 5 to 10 mg/cm platinum, a surface temperature of up to l,600C is obtained according to the higher reaction.

in accordance with a particularly preferred embodiment of this method, the nickel salts used for forming catalysts can also be doped with uranium compounds in order to increase the stability. These compounds,

during the combustion process, convert into uranium' oxide UO and in this form help to produce active centers in the catalyst. For doping purposes, additions of l to 3 percent-by weight uranium oxide, relative to the catalyst content. are sufficient.

It was found that according to the suggested method, the gas mixture which is obtained during the incomplete and flameless combustion of hydrocarbons may be employed particularly expediently for obtaining hydrogen. This is of advantage especially when a small construction is indicated for the hydrogen producing system, which is frequently the case in fuel cell plants.

into the reaction gases. At the same time, a cooling of the reaction gas and an evaporation of the water takes place.

During the incomplete, flameless combustion according to the previously suggested method, the air or oxygen volume is such that reaction takes place according to the equation:

Contrary to known hydrocarbon combustion, the reaction proceeds even without the addition of water vapor without soot, which is important for the practical execution of the method. It occurs mainly in the sinter block impregnated with nickel or platinum.

According to the invention, the gases formed during the incomplete combustion (CO, H, and slight amounts By quenching, we mean here, the injection of water the sinter of CO are reacted catalytically with water vapor, according to the equation:

at temperatures between 150 and 500C. The catalysts may be any of the known conversion catalysts. such as for example. mixtures of zinc and copper or iron and chromium. Particularly effective were the mixtures of zinc. copper. chromium and slight amounts of ironsThe indicated catalysts may also be employed in oxidized form or in mixtures, with oxides.

The method of the invention. as well as a device for performing said method, will now be disclosed in greater detail with reference to the Drawing, in which:

amount is so rated that the combustion remains incom-.

plete. It takes place in the sinter block 7, impregnated with nickel or platinum. The resultant gases subsequently pass the porous sinter block 8, which serves as a radiation protection and is a catalyst-free. porous sinter block. provided with passage openings. ln chambers 9, 10. 11 and 12, the gas mixture is then mixed, stepwise. with the water volume necessary for the conver sion and the carbon monoxide is converted into carbon dioxide in the sinter blocks l3, l4, l5, l6, containing the catalyst, according to equation:

At the same time, a temperature gradient occurs along blocks 13 to 16. so that conversion takes place in sinter blocks 13 and l4, at temperatures of about 350 to-500C and in sinter blocks 15 and 16, at temperatures from 200 to 280C. The supply of water into the injection chambers 9 to 12 is effected via the ribbed pipe system 17, the collecting pipe 18 and the branch pipes 19, 20, 21 and 22. The water is simultaneously being preheated in the tubular system 17.

The resulting raw gas leaves the hydrogen producing installation, according to the invention, via line 23 and comprises carbon dioxide and hydrogen. The carbon dioxide is removed from the gas by means of suitable absorbants in known manner.

1n the Drawing. the numeral 24 denotes the housing, 25 the interior lining and 26 the housing insulation. while 27 represents the outer insulation of the suction channel 2.

As previously mentioned. all catalysts known to be suitable for this purpose may be employed as conversion catalysts. 1n the Examples the catalyst consisted of a copper-zinc mixture.

In the hydrogen producing installation according to the invention. 58.9 Nm" air (or 7.85 Nm oxygen) were sucked in per hour. through duct 2 and mixed with the injected benzene. in chamber 4. There were 10 kg, perhour. benzene injected into the chamber 4. During the 4 contains platinum. the temperature of the mixture rose to about 1.250C. This resulted, per hour. in 7.85 Nm CO. 7.85 Nm CO 17.6 Nm H, and 47.2 Nm N (or 15.7 Nm CO and 17.6 Nm H when 0 was used). By injecting about 40 liters water. per hour (or 15 liters per hour when 0 was used) a drop in the temperature of the reaction mixture to approximately 350C was effected. 1n conversion sinter blocks 13 to 16, a gradual reaction of the carbon monoxide now takes place with development of heat. About 15 liters water (5 liters water when 0 was used) are also injected into the chambers 10, 11 and 12, whereby the reaction temperature drops to about 200C, in the last stage.

In the above Example, it was possible to produce 25.5 Nm hydrogen per hour (or 34 Nm hydrogen per hour when 0 was used) per 10 kg benzene, initial feed.

The dimensions of the hydrogen producing installation were 844 mm. 131 mm width and 155 mm height.

The device for producing hydrogen by means of sootfree conversion of hydrocarbons with oxygen or air and water vapor, is characterized primarily through its low space requirement and is therefore particularly suitable for such installations which are supposed .to be small in size such as, for example, for hydrogen producing installations of portable fuel cell batteries. The device shown in the FIGURE is suitable. however, not only for producing hydrogen but also for the production of inert gas. for example, nitrogen. When nitrogen is obtained from air, it is preferable to employ the benzene and air mixture in a stoichiometric ratio so that only CO is ensuing catalytical combustion in sinter block 7, which present in a raw gas mixture, in addition to nitrogen. The CO may be washed out, in a known manner, with the aid of an absorption liquid.

The method according to the invention can also be used for converting carbon monoxide contained in the exhaust gases of motor vehicles, whereby the injection 1 claim:

1. A device for obtaining a gas mixture containing hydrogen and carbon dioxide by incomplete, catalytic combustion of a hydrocarbon and oxygen containing gas mixture and subsequent catalytic conversion of the obtained gas mixture. containing CO and H by adding water. which comprises a common housing with inlet ducts for hydrocarbons andoxygen and an outlet duct for the gas mixture containing hydrocarbon and carbon dioxide. at least two highly porous sintered blocks with parallel openings between said inletand outlet ducts, said sintered blocks being positioned in flow direction, one behind another. at such spacing that a free space is formed therebetween. the first of said sintered blocks. in flow direction, being provided with a catalyst for incomplete flameless combustion of the hydrocarbon and oxygen containing gas mixture and at least the last of said sintered blocks. in flow direction, being provided with a catalyst for converting the CO and H, containing gas mixture and means for injecting liquid water into the free space positioned ahead of the sintered blocks provided with converting catalyst.

2. The device of claim 1, wherein a catalyst-free sintered block provided with passage openings is arranged in the oxygen inlet duct in flow direction ahead of the first sintered block, a free space is formed between the catalyst-free block and the first sintered block and the inlet duct for hydrocarbons ending in said free space.

preheating at least one of the hydrocarbons, the water and the oxygen are provided behind the last sintered block in flow direction provided with converting catalyst.

5. The device of claim 1, wherein nickel is provided as the combustion catalyst.

6. The device of claim 1, wherein platinum is provided as combustion catalyst.

7. The device of claim 5, wherein the combustion catalyst is doped with uranium oxide.

8. The device of claim 6, wherein the combustion catalyst is doped with uranium oxide.

9. The device of claim 1, wherein a mixture of at least two of the substances selected from the group consisting of zinc, copper, chromium and iron is provided in metallic or oxidic form as the converting catalyst. 

2. The device of claim 1, wherein a catalyst-free sintered block provided with passage openings is arranged in the oxygen inlet duct in flow direction ahead of the first sintered block, a free space is formed between the catalyst-free block and the first sintered Block and the inlet duct for hydrocarbons ending in said free space.
 3. The device of claim 1, wherein between the sintered block provided with combustion catalyst and the first sintered block provided with the converting catalyst, an additional sintered block having passage openings is arranged at such distance from both sintered blocks that a free space forms between said sintered blocks and means for injecting liquid water into the free space between said additional sintered block and the first sintered block provided with the converting catalyst.
 4. The device of claim 1, wherein heat exchangers for preheating at least one of the hydrocarbons, the water and the oxygen are provided behind the last sintered block in flow direction provided with converting catalyst.
 5. The device of claim 1, wherein nickel is provided as the combustion catalyst.
 6. The device of claim 1, wherein platinum is provided as combustion catalyst.
 7. The device of claim 5, wherein the combustion catalyst is doped with uranium oxide.
 8. The device of claim 6, wherein the combustion catalyst is doped with uranium oxide.
 9. The device of claim 1, wherein a mixture of at least two of the substances selected from the group consisting of zinc, copper, chromium and iron is provided in metallic or oxidic form as the converting catalyst. 